At the beginning of the year, manufacturing overhead for the year was estimated to be $350860. At the end of the year, actual direct labor-hours for the year were 50800 hours, the actual manufacturing overhead for the year was $545860, and manufacturing overhead for the year was underapplied by $20820. If the predetermined overhead rate is based on direct labor-hours, then the estimated direct labor-hours at the beginning of the year used in the predetermined overhead rate must have been: